1. Field of the Invention
The present invention generally relates to radio frequency propagation devices and, more particularly, to a waveguide device for propagating radio frequency signals in planar circuits, including the concurrent transmission of signals of different polarizations.
2. Description of the Related Art
In general, compact electronic systems are made up of functional modules, such as local oscillator, signal processing, power, and/or control modules. Such functional modules are typically mounted on different layers of a single multi-layer circuit to provide compact systems. Mounting functional modules on different layers within a circuit, however, requires the use of multi-layer interconnects. For low frequencies, different layers can be connected using vias or coaxial lines. For microwave and millimeter-wave frequencies, different layers are presently connected using actual connectors, such as subminiature type A (SMA) connectors. The use of such connectors, however, increases the system cost and limits design flexibility.
In addition, some electronic systems, particularly electronic communication systems, provide for concurrent transmission of signals of different polarizations and/or different frequencies through a common channel in order to use the frequency spectrum efficiently. Thus, a transmitter circuit would use one polarization while a receiver circuit would use another. If the transmitter and receiver circuits are on different layers in a multi-layer circuit, an orthomode transducer (OMT) is required to connect the layers to a common input/output. An OMT typically connects the transmitter and receiver circuits through interconnects that employ actual connectors or waveguide flanges. Such connections result in bulky metal structures that are not convenient for integration into compact multi-level electronic circuits.
Therefore, there exists a need in the art for a device for efficient propagation of radio frequency (RF) signals, including concurrent transmission of signals of different polarizations, in planar circuits.
The present invention generally provides a device for efficient propagation of RF signals, including concurrent transmission of signals of different polarizations, in planar circuits. In one embodiment, an orthomode transducer comprises a waveguide having an input port for receiving electromagnetic radiation having a first polarized signal and a second polarized signal, the first and second polarized signals being orthogonal to one another. The waveguide includes first and second substrates mounted therein and positioned transverse to the longitudinal axis thereof. Both the first and second substrates are substantially transmissive of the electromagnetic radiation. The first substrate includes a probe formed thereon for transmitting or receiving the first polarized signal, and the second substrate includes a probe for transmitting or receiving a second polarized signal. The probe on the first substrate is oriented parallel to the polarization vector of the first polarized signal, and the probe on the second substrate is oriented parallel to the polarization vector of the second polarization vector. A grid substrate is mounted in the waveguide between the first and second substrates and positioned transverse to the longitudinal axis thereof. The grid substrates includes a multiplicity of metallic lines disposed in a spaced apart relation and oriented to be reflective of the first polarized signal and transmissive of the second polarized signal.
In a second embodiment, an apparatus for interconnecting a plurality of planar circuits comprises a waveguide for propagating electromagnetic radiation, a first substrate, and at least one additional substrate. The first and additional substrates are mounted within the waveguide and are positioned traverse to the longitudinal axis thereof. The first and additional substrates are substantially transmissive of the electromagnetic radiation. The first substrate includes a probe formed thereon for transmitting the electromagnetic radiation. The additional substrates include probes formed thereon oriented in the same direction as the probe on the first substrate for receiving the electromagnetic radiation transmitted therefrom.